I went to an event at Willow Springs that was put on by these guys:
Extreme Speed Track Events
Sometimes they do special pricing where its only $75 per day, which is pretty awesome.
They do self tech events, so I think you'de be able to skate by with an oil leak, since they dont actually look at your car....but yeah, for most other track events, i think they inspect your car to see if it meets their standards...which includes no oil leaks.
But yeah...sounds like your clutch is pretty funky. Wheres your oil leak coming from?